The SOI symmetric lateral bipolar transistor is uniquely suitable for operation at high injection currents where the injected minority carrier density in the base region is larger than the base doping concentration. Transistors operating in high-injection can achieve record-high drive currents on the order of 3-5 mA/μm. The commonly used Shockley diode and bipolar current equations are modified to be applicable for all injection levels. Excellent agreement is shown between measured and modeled currents for data at VBC = 0. A novel partially depleted-base design can further increase the drive current and the current gain, especially at low VBE.